Temperature Dependence of Anisotropic-Ultrasonic Propagation in a Nematic Liquid Crystal

The ultrasonic attenuation and velocity of longitudinal waves in the nematic liquid crystal $N-p$-methoxybenzylidine-$p$-butylaniline have been measured as a function of temperature and applied magnetic field at 3.5 MHz, between 17 and 65°C. The orientational anisotropy of the attenuation is strongly temperature dependent in the nematic phase. The velocity shows a 9% dip in the region of the transition; no anisotropy was observed within the 1% accuracy of the measurements.